Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization

Recovery after Unilateral Phrenic Injury Associated with Coronary Artery RevascularizationHemidiaphragmatic paralysis has been reported to occur in approximately 10 percent of patients after CAB surgery. The phrenic nerves are vulnerable to injury during CAB surgery because of their proximity to the heart. Several mechanisms have been proposed to explain a phrenic nerve paresis or paralysis during CAB surgery. Inadvertent sectioning might occur during bypass surgery; however, this appears to be an uncommon event. More importantly, the phrenic nerve can be stretched or compressed during the mobilization and exposure of the heart or with dissection of the internal mammary artery when used for implant. This could result in either direct nerve trauma or indirect damage secondary to compromise of the vascular supply of the phrenic nerve. Scannell first proposed another form of nerve injury during CAB surgery: a hypothermic injury related to the use of topical cold cardioplegia. In this technique, saline slush is placed into the pericardium in an attempt to reduce myocardial oxygen consumption. The phrenic nerve is separated from the slush by only a thin layer of connective tissue which likely affords little insulation. buy asthma inhalers
To date, the rate and extent of recovery of the phrenic nerve after paralysis related to bypass has not been accurately quantitated. In this study, we performed repetitive phrenic nerve electrophysiologic studies along with measurements of lung volumes and ventilatory muscle strength in five patients who developed phrenic nerve paresis or paralysis after CAB surgery. This facilitated a characterization of phrenic nerve recovery and an evaluation of the functional effects of phrenic nerve injury.